ABIDJAN, May 29 (Reuters) - As the afternoon sun glinted offthe waters in Ivory Coast's port of Abidjan, a team of gendarmesset out in a leaky wooden pirogue with no weapons and nothingmore than mobile phones for communication.

Their mission: to hold the front line against piracy in theworld's new hotspot for maritime crime, the Gulf of Guinea offthe coast of West Africa.

"This is how we work every day," grumbled one man as theiroutboard motor sputtered out, setting them adrift amid bobbingplastic bottles. "We don't even have life vests."

Until recently, Ivory Coast's maritime surveillance brigade- the equivalent of a coastguard - managed, barely, to keep alid on crime in the waters around one of Africa's busiest ports.

But ruthless Nigerian gangs, which have expanded hundreds ofmiles beyond their home waters in the last three years, reachedfrancophone West Africa's largest economy in October.

Born of an uprising in Nigeria's oil-rich Niger Delta, whichspawned a web of criminal networks, the gangs now threaten toderail the development of one of the world's poorest regions asthe Gulf of Guinea seeks to become a major oil and gas hub.

The start-up of large oil fields in Ghana, and promisingdiscoveries to the west in neighbouring Ivory Coast, have helpedto stoke interest in the region from international oil firms.

The spike in attacks is alarming Western powers, not leastthe United States, as regional governments struggle to cope.

In 2010, the International Maritime Bureau (IMB), which hasmonitored global piracy since 1991, recorded 33 attacks in theGulf of Guinea. Last year, that figure jumped to 58.

Analysts say widespread under-reporting means the figurereflects just a fraction of the total, as there is little hopeof rescue and reporting attacks bumps up insurance premiums.

"We estimate there is about one attempted or actual pirateattack a day ... with the chance of it going to almost two a dayif present trends continue," said Michael Frodl, head ofU.S.-based consultancy C-Level Maritime Risks.

"It would be a slaughter ... What can we do against that?"said Captain Augustin Dago, the man tasked with leading themaritime surveillance brigade. "We're just hoping it doesn't getany worse: that what's happening off Somalia doesn't come toIvory Coast."

NOT SOMALIA

After eight years and nearly 150 hijackings, Somali pirates'stranglehold over East Africa's busy shipping lanes, which theWorld Bank says may cost the global economy $18 billion a year,is now being brought under control.

Armed attacks, once counted in the hundreds, fell to 75 in2012, according to the IMB. Somali pirates have succeeded inseizing just one vessel off the Horn of Africa so far this year.

The world's mightiest navies and security firms hired byshipping companies were given a free hand off Somalia and theirrobust tactics are credited with stamping out piracy there.

"Whereas in Somalia, we faced an absence of government, inthe Gulf of Guinea the exact opposite holds true," AndrewShapiro, U.S. Assistant Secretary of State forPolitical-Military Affairs, told a congressional sub-committeelast month.

"There are many sovereign governments with varying degreesof capability but all with their own laws, their own interests."

For many West African governments, suspicious of foreignmeddling, a massive influx of warships is a non-starter. Andmost regional nations - often states recovering from brutalcivil wars - ban the use of weapons by private security details.

Until now, the greatest obstacle to solving the problem inthe Gulf of Guinea has been a lack of interest.

"If you look at the operations in East Africa and thecapacity they brought and the money they threw at it, they'venot touched anything like that here," said Johan Potgieter, aresearcher at Pretoria's Institute for Security Studies.

ROOTS IN NIGERIA

The United States began monitoring the gangs emerging fromthe Niger Delta early on and with growing concern. In 2010, Nigeria and Angola - the region's two top oil producers -accounted for nearly 15 percent of U.S. oil imports.

Styling themselves as fighters for independence, but withall the hallmarks of a criminal mafia, groups such as theMovement for the Emancipation of the Niger Delta (MEND) had foryears made big money taking oilmen hostage and bunkering -selling crude oil illegally siphoned from pipelines onto theblack market.

By 2009, when Nigeria offered the militants an amnesty in abid to end the violence that was crippling oil output, they werealready extending their activities east into the waters ofCameroon.